Overview
This page defines each SEO term once, in one or two sentences, and links to the deep-dive page where one exists. It is the citation anchor for the other SEO pages, grouped by domain so a developer or editor can scan a section.
Core search concepts
What is SEO (Search Engine Optimization)?
SEO is the practice of improving a site’s organic visibility in search engines through technical setup, content quality, structured data, and earned links. See technical and content.
What is a SERP (Search Engine Result Page)?
A SERP is the page a search engine returns for a query: organic results, ads, and features such as featured snippets and People Also Ask. See serp-features.
What is a search engine?
A search engine is a system that crawls, indexes, and ranks web pages. AI answer engines such as ChatGPT Search, Perplexity, and Google AI Mode retrieve and cite pages differently. See generative-engine-optimization.
What is search intent?
Search intent is what the searcher wants from a query: informational, navigational, commercial investigation, or transactional. Matching intent decides the page format. See content.
Crawling and indexing
What is a crawler?
A crawler is a bot that fetches pages to discover content. Googlebot, Bingbot, and Applebot index for search; AI vendors run their own, such as GPTBot, ClaudeBot, and PerplexityBot. See javascript-seo.
What is crawl budget?
Crawl budget is the number of URLs a search engine will fetch from a site in a period, and Google says it matters mainly for very large or fast-changing sites. See crawl-budget and crawl-budget.
What is indexing?
Indexing is parsing a fetched page and storing it in the search index. Only indexed pages can rank.
What is the page indexing report?
The page indexing report in Google Search Console, formerly Index Coverage, shows which URLs are indexed and why others are not. It is the first place to check when traffic drops. See master-google-search-console.
What is noindex?
Noindex is a robots meta tag or X-Robots-Tag header that asks search engines to exclude a page from the index. The page must stay crawlable for the tag to be seen.
What are nofollow, ugc, and sponsored?
They are rel link attributes that Google treats as hints: nofollow for untrusted links, ugc for user-generated content, and sponsored for paid placements.
What is mobile-first indexing?
Mobile-first indexing means Google indexes the mobile version of a page. Google declared the switch complete in October 2023. See mobile-first.
On-page SEO
What is a title tag?
A title tag is the HTML <title> element, a main source for the title link shown in results. Google rewrites titles that are vague, stuffed, or mismatched to the content. See title-tags.
What is a meta description?
A meta description is the <meta name="description"> tag that can supply the result snippet. It is not a direct ranking signal but influences clicks. See write-meta-descriptions.
What is a canonical URL?
A canonical URL is the one URL chosen as the indexable version of a page, declared with <link rel="canonical"> and treated by Google as a hint. Self-referential canonicals on indexable pages prevent parameter and protocol duplicates. See canonical-url and redirects.
What is anchor text?
Anchor text is the visible text of a link. Descriptive anchors beat “click here” for search and accessibility. See internal-linking.
What is keyword stuffing?
Keyword stuffing is cramming keywords into a page beyond natural use. It is listed in Google’s spam policies and can be demoted algorithmically or draw a manual action.
What is a long-tail keyword?
A long-tail keyword is a multi-word, lower-volume query that is usually easier to rank for and has one clear intent. See keyword-research.
What is cannibalization?
Cannibalization is two pages on one site competing for the same query so neither wins. See cannibalization.
Off-page SEO
What is a backlink?
A backlink, or inbound link, is a link from another site to yours, and the original PageRank signal. The quality and relevance of the referring site matter more than the count. See backlinks.
What is an internal link?
An internal link points from one page on your site to another, and is the strongest link lever you control. See internal-linking.
What is a referring domain?
A referring domain is a unique domain that links to your site. Links from many distinct domains are a stronger signal than many links from one.
What is disavow?
Disavow is a Search Console tool for asking Google to ignore listed links. Google says most sites do not need it and to use it only when spammy links caused, or will likely cause, a manual action. “Toxic backlink” is an SEO-tool label, not a Google term. See backlinks.
Technical SEO
What is robots.txt?
robots.txt is a root file that declares crawl scope to bots. See discoverability-files.
What is sitemap.xml?
sitemap.xml is an XML file listing canonical URLs with their lastmod. See discoverability-files.
What is a 301 redirect?
A 301 is a permanent redirect and a strong signal that the target should be canonical. Google’s Gary Illyes said in 2016 that 30x redirects do not lose PageRank. See redirects.
What are 302, 307, and 308 redirects?
A 302 is a temporary redirect, used for A/B tests and outages, and the original URL stays the canonical candidate. 307 and 308 are the method-preserving counterparts of 302 and 301.
What is a soft 404?
A soft 404 is a 200 response on a page with no real content, such as empty search results. Google detects and excludes these. Return a real 404.
What is hreflang?
Hreflang is an annotation declaring language and region variants of a page. See hreflang.
What is faceted navigation?
Faceted navigation is filter UI (color, size, price) that generates parameterized URLs, and without crawl control it creates a combinatorial explosion of near-duplicate pages. See pagination-and-facets.
What is pagination?
Pagination splits a long list across numbered pages. Use a self-canonical on each page; Google no longer uses rel="prev" and rel="next". See pagination-and-facets.
Structured data
What is Schema.org?
Schema.org is the shared vocabulary for structured data, supported by Google, Bing, Yandex, and others.
What is JSON-LD?
JSON-LD is the structured data format Google recommends: a <script type="application/ld+json"> block, usually in <head>. See structured-data.
What is a rich result?
A rich result is a listing enhanced by structured data, such as ratings or recipe cards. Google has retired several types, including HowTo, the sitelinks search box, and FAQ. See structured-data and schema-markup-deep.
What is Article schema?
Article schema is the JSON-LD type for editorial pages. Google lists no required properties; headline, datePublished, dateModified, author, and image are the usual set. See e-e-a-t.
What is FAQPage schema?
FAQPage schema declares question-and-answer pairs. Google stopped showing FAQ rich results on May 7, 2026; the markup is still valid schema.org and harmless on genuine Q&A pages. HowTo rich results were removed in September 2023. See schema-markup-deep.
What is sameAs?
sameAs is a schema.org property listing public profile URLs (LinkedIn, GitHub, Wikipedia, Wikidata) that identify the same entity. It aids entity resolution.
Performance and Core Web Vitals
What are Core Web Vitals (CWV)?
Core Web Vitals are Google’s three field-measured experience metrics: LCP, INP, and CLS, judged at the 75th percentile. See core-web-vitals and core-web-vitals.
What is LCP (Largest Contentful Paint)?
LCP is the time to render the largest above-the-fold element; good is 2.5 seconds or less. See lcp.
What is INP (Interaction to Next Paint)?
INP measures the delay from a user interaction to the next visual update; good is 200 ms or less. It replaced FID in March 2024. See inp.
What is CLS (Cumulative Layout Shift)?
CLS scores unexpected layout shifts; good is 0.1 or less. See cls.
What is TTFB (Time to First Byte)?
TTFB is server response time. It is not a Core Web Vital; good is 800 ms or less. See page-speed.
What is Lighthouse?
Lighthouse is Google’s lab tool for auditing performance, accessibility, SEO, and best practices. Lab data is for development, not a ranking verdict. Its agentic browsing category also checks for llms.txt.
AI search and agent readability
What is AEO (Answer Engine Optimization)?
AEO is optimizing content so AI answer engines can extract and cite it. Google’s guide treats it as SEO. See generative-engine-optimization.
What is GEO (Generative Engine Optimization)?
GEO is the same practice under a name that emphasizes generative engines. Bing’s guidelines define it as content eligibility for grounding and reference in AI responses. See generative-engine-optimization.
What is an AI Overview?
An AI Overview is Google’s AI-generated summary above the results for some queries, with links to sources. No special markup or AI text file is needed. See ai-overviews.
What is AI Mode?
AI Mode is Google’s conversational AI search experience for complex questions, which answers with links to supporting sites and, since I/O 2026, runs as one flow with AI Overviews. See ai-overviews.
What is query fan-out?
Query fan-out is the technique AI Overviews and AI Mode use to issue several related searches across subtopics before composing an answer.
What is llms.txt?
llms.txt is a proposed markdown index at the site root that agents can ingest cheaply; the optional llms-full.txt carries full page text. Google Search ignores both. See llms-txt and llms-txt.
What is ai.txt?
ai.txt is a proposed file declaring AI usage preferences at the domain level. See ai-txt and ai-txt.
What are GPTBot, ClaudeBot, and PerplexityBot?
They are the crawlers of OpenAI, Anthropic, and Perplexity. GPTBot and ClaudeBot collect training data, while PerplexityBot indexes for Perplexity search; each vendor documents robots.txt support and none documents reading ai.txt. See ai-crawlers.
What is Google-Extended?
Google-Extended is a robots.txt product token, not a crawler, so it never appears in logs. It controls whether Googlebot-fetched content is used for Gemini training and grounding, and it does not affect Search, AI Overviews, or AI Mode.
What is entity SEO?
Entity SEO is building a recognized entity (author, brand, product) that engines can resolve and connect. See e-e-a-t.
What is a knowledge graph?
A knowledge graph is a search engine’s structured database of entities and their relationships, which drives knowledge panels.
Content strategy
What is topical authority?
Topical authority is the depth and breadth of a site’s coverage of a topic. It is built by publishing focused, original content on one subject. See content-clusters.
What is a content cluster?
A content cluster is a pillar page plus supporting cluster pages, all internally linked. The pillar covers the head topic broadly; each cluster page answers one sub-question. See content-clusters.
What is E-E-A-T?
E-E-A-T stands for Experience, Expertise, Authoritativeness, and Trustworthiness, the rubric in Google’s quality rater guidelines. It is not a single ranking factor. See e-e-a-t and e-e-a-t.
What is the helpful content system?
The helpful content system was Google’s 2022 classifier for people-first content. It became part of core ranking in March 2024, so no standalone update exists. See core-updates.
What is helpful content (people-first content)?
Helpful content, or people-first content, is Google’s term for content written to answer the searcher rather than to rank. Its opposite is search-engine-first content. See core-updates.
What is a content refresh?
A content refresh is a substantive update to an existing page, as opposed to a date-only change. See content-refresh.
What is YMYL (Your Money or Your Life)?
YMYL covers topics where bad information could significantly affect health, financial stability, or safety. Google gives E-E-A-T more weight there.
Discoverability files
What are discoverability files?
Discoverability files are the special files a public site ships at the root or under /.well-known/, such as robots.txt, sitemap.xml, llms.txt, security.txt, and the manifest. See discoverability-files.
What is security.txt?
security.txt, defined in RFC 9116, is a file at /.well-known/security.txt that gives researchers a vulnerability disclosure contact.
What is IndexNow?
IndexNow is a protocol for notifying participating search engines, such as Bing and Yandex, of content changes. The site proves ownership with a key file at /<key>.txt. See indexnow and indexnow.
What is an OG image?
An OG image is the og:image social preview image, conventionally 1200x630. See og-images.
SERP features
What is a featured snippet?
A featured snippet is a result that shows a direct answer above the first organic listing. See serp-features.
What is People Also Ask (PAA)?
People Also Ask is the expandable question list in the middle of a SERP. See serp-features.
What is a local pack?
A local pack is the map plus three business listings for local queries, driven by Google Business Profile. See local-seo.
Penalties and recovery
What is a manual action?
A manual action is a penalty applied by a Google human reviewer and reported in Search Console. After fixing the issue, submit a reconsideration request to clear it.
What is an algorithmic demotion?
An algorithmic demotion is a ranking change applied by Google’s systems, with no notification, detected through traffic patterns.
What is a core update?
A core update is a broad change to Google’s ranking systems, listed on the Search Status Dashboard when it starts and when it completes. See core-updates and algorithm-history.
Local SEO
What is Google Business Profile (GBP)?
Google Business Profile is the free Google product for managing a business’s local listing, formerly Google My Business. See local-seo.
What are NAP and citations?
NAP is name, address, and phone, which should match across the site and profile. A citation is a mention of that NAP on another site, such as Yelp or Bing Places. See local-seo.
Analytics and tooling
What is Google Search Console (GSC)?
Google Search Console is Google’s free tool for monitoring search performance, indexing, and structured data. See master-google-search-console.
What is Bing Webmaster Tools?
Bing Webmaster Tools is Microsoft’s equivalent, and includes the AI Performance report for Copilot citations. Pair it with Search Console. See ai-citation-tracking.
What is CTR (Click-Through Rate)?
CTR is the share of impressions that result in a click, the main measure when testing titles and descriptions.